Whether this is caused by ageing, accident, an injury or a trauma, the present invention gives the possibility of assisting a user by correcting his/her movements in order to:                help him/her recover a body function which was altered (for example in order to again find the use of a hand after repair surgery), or at the very least        to teach him/her to adapt to a new condition (teach a person amputated of a lower limb to walk with a prosthesis, a person victim of a stroke, etc.).        
Devices and assumed methods are known for helping a user to recover a body function. Document WO 2008/132324 describes a method for measuring and correcting the postural vertical position of a human being. This device comprises a camera, a viewing screen and processing means. The operating principle of such a device is the following:                the user is installed in a sitting position without any back seat,        two markers are positioned in his back along his/her spine,        the camera is installed behind the user so as to acquire images of his/her back,        the viewing screen is installed in front of the user so that he/she may observe the images displayed on said screen, finally        the processing means are connected to the camera and to the display screen.        
Once the installation is finished, the camera is enabled in order to acquire images of the back of the user. These images are transmitted to the processing means giving the possibility of estimating a tilt of the patient's back relatively to the vertical. The processing means then control the display on the viewing screen:                of a schematic illustration of the user,        of his/her tilt relatively to the vertical, modelled by the line segment between both markers, and        of a deviation angle value of said tilt.        
Such a device has many drawbacks. On the one hand, the installation of the device on the whole is tedious and may not be applied by the user him/herself. Indeed, the installation of markers in the user's back and the positioning of the camera requires the presence of a person for assisting the user. Further, the complexity of setting into place the device makes the use of the latter prohibitive. The rehabilitation exercises being generally tedious to carry out for the user, the setting into place of devices assumed to help him/her should be as simple as possible so as not to discourage him/her and to allow observance of the prescribed and required rehabilitation.
Another drawback of this device is that the information displayed on the viewing screen is not sufficiently intuitive so as to allow him/her to correctly correct his/her posture. Notably, the observation of his/her tilt relatively to the vertical may incite the user to force on his/her muscles excessively for aligning his/her back on the vertical. Now, studies have shown that the level of difficulty of rehabilitation exercises should be progressive and that excessive rehabilitation may have adverse consequences. For example, knee flexure exercises according to a too-large angle after surgery of crossed ligaments may induce an irreversible degradation of the properties of the ligaments.
Further another drawback of this device is that the pieces of information displayed on the screen do not allow the user to apprehend his/her progression during his/her rehabilitation. Indeed, even if the display of a deviation angle value is a piece of relevant information for a practitioner, it is not for a layman user. Finally, the device described in WO 2008/132324 does not allow adaptation of the rehabilitation exercises according to the user.
U.S. Patent Publication No. 2011/0021318 describes a device for training the motor control of a user. U.S. Pat. No. 7,867,140 describes a device for correcting the motor coordination of a user. These devices have the same drawbacks as the device described in WO 2008/132324.
An aim of the present invention is to propose a device and a method giving the possibility of overcoming at least one of the aforementioned drawbacks.